1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a LCD device having color filters arranged in quad type.
2. Description of Related Art
In general, the LCD device includes a liquid crystal panel having upper and lower substrates with a liquid crystal layer interposed. The upper substrate includes a common electrode and a color filter. The lower substrate is called an array substrate and includes gate lines arranged in a transverse direction and data lines arranged in a longitudinal direction perpendicular to the gate lines. A pixel electrode is formed on a region defined by the gate and data lines. Thin film transistors (TFTs) as a switching element are formed at a crossing point of the gate and data lines. Each of the TFTs includes a gate electrode, a source electrode and a data electrode. Peripheral portions of the two substrates are sealed by a sealant to prevent a liquid crystal leakage. The gate line serves to transmit scanning signals to the gate electrode, and the data line serves to transmit data signals to the source electrode.
In such an LCD device, a drive integrated circuit (IC) that applies signals to each electrode line on the lower substrate may be mounted using various methods, for example, a chip on board (COB), a chip on glass (COG), a tape carrier package (TCP), and the like.
FIG. 1 is a cross-sectional view illustrating a liquid crystal panel having a drive IC mounted thereon using the TCP technique. As shown in FIG. 1, a drive IC 17 is mounted on a polymer film 19, and the polymer film 19 having the drive IC 17 is connected with both a lower substrate 11 and a printed circuit board 15 through an anisotropic conductive film (AFC) 18. Signals are applied through such a tape carrier package from each end portion of gate and data lines (not shown) to drive the liquid crystal panel having the lower and upper substrates 11 and 13.
In a large-sized LCD device employing the TFT as a switching element, when a direct current bias is applied to the liquid crystal layer, the liquid crystal layer can be deteriorated. Thus, it is preferable to change a polarity of a voltage applied to the liquid crystal layer for each frame. Such an inversion driving method is classified into a frame inversion driving, a column inversion driving, a line inversion driving, and a dot inversion driving.
FIGS. 2A to 2D are plan views illustrating the four inversion methods described above. In the frame inversion driving method, as shown in FIG. 2A, all of the pixels receive signals of the same polarity in one frame and in next frame all of the pixels receive signals of inverse polarity. FIG. 2B illustrate the column inversion driving method, that pixels of every other column receive the signals of the same polarity and the polarity of the signal is changed at the next frame. FIG. 2C illustrate the line inversion driving method, that pixels of every other line (row direction) receive the signals of the same polarity and the polarity of the signal is changed at the next frame. FIG. 2D illustrate the dot inversion driving method. In the dot inversion drive method, the drive voltages applied to the pixel electrodes are such that the polarities of the adjacent two pixel electrodes, which are disposed adjacent to each other in either column or row direction, with respect to the counter electrode are opposite to each other. In other words, the polarities of the pixel electrodes with respect to the counter electrodes alternate as viewed along both the column direction and the row direction at each instance
Through such inversion methods, a cross talk and a flickering of a screen can be reduced and a large-sized color LCD device is driven using such a method.
In order to drive the LCD device, gate drive ICs and data drive ICs, which are respectively connected with data lines and gate lines, are mounted to the liquid crystal panel through various method described above. Further, the LCD device employs either of a dual bank structure and a single bank structure to drive the liquid crystal layer. The dual bank structure is one that the data drive ICs are arranged on both upper and lower portion of the liquid crystal panel, and the single bank structure is one that the data ICs are arranged on either of the upper and lower portion of the liquid crystal panel.
FIG. 3 is a plan view illustrating a conventional quad type color LCD device. A liquid crystal panel 113 generally includes 1024×1024 number of dots, and a unit pixel includes four sub pixels or dots: a red (R), a green (G), a green (G), and a blue (B) as shown in FIG. 3. In order to drive the 1024×1024 number of dots, gate and data drive ICs have 1024 number of channels, respectively. The two gate drive ICs 113a are arranged on a left side portion of the liquid crystal panel 111, and two gate drive ICs 113b are arranged on a right side portion of the liquid crystal panel 111 in a dual bank method. Each of the gate drive ICs 113a and 113b has 256 channels. Also, the four data drive ICs 115a are arranged in an upper portion of the liquid crystal panel 111, and the four data drive ICs 115b are arranged in a lower portion of the liquid crystal display panel 111 in a dual bank method. Each of the data drive ICs 115a and 115b has 128 number of channels. The liquid crystal display panel 111 can employ the dot inversion driving method and the frame inversion driving method. An external controller can control such driving methods.
FIG. 4 is a plan view illustrating data signal transmissions of the liquid crystal panel having a dual bank structure according to a conventional art. As shown in FIG. 4, the data drive ICs 115a arranged in the upper portion of the liquid crystal panel 111 to drive odd data lines 121, and the data drive ICs 115b arranged in the lower portion of the liquid crystal panel to drive even data lines 123. Therefore, a difference of a signal delay due to a line resistance between the odd and even data lines may occur. For example, a difference of a signal delay between the adjacent two odd and even data lines may occur at portions A and A′. As a result, optical characteristics of the pixel may vary, whereby defects due to a brightness difference may occurs at the portions A and A′. In the liquid crystal panel described above, the gate and data drive ICs are arranged on side portions, and thus, the liquid crystal should be injected through a corner portion of the liquid crystal panel in a vacuum atmosphere using a dip method. However, the dip method may cause a contamination problem, and also a large amount of the liquid crystal is required.
In order to overcome the problems of difference of signal delay and the injection of the liquid crystal, a single bank data driving method has been introduced. The single bank data driving method is one that the data drive ICs are arranged on either of the upper and lower portions of the liquid crystal panel. FIG. 5 is a plan view illustrating a configuration of a liquid crystal panel having the single bank structure according to another conventional art. Three number of the data drive ICs 115 having 384 channels are arranged in the upper portion of the liquid crystal panel in order to drive 1024 number of the data lines. At this time, since the three data drive ICs have all 1152 number of channels, each of outmost data drive ICs 115c and 115d has 64 number of dummy channels. The dummy channels are from first channel to sixty fourth channel and a first effective channel is the sixty fifth channel. At this point, the data drive IC applies signals “+, −, +, − . . . ” in series from the first channel, and next signal of series can be selected in the form of either “+, −, +, − . . . ” or “−, +, −, + . . . ” by an external controller. Thus, the inversion methods shown in FIGS. 2B and 2D can be established. But, the frame inversion for quad type color filters illustrated in FIG. 2A cannot be established. That is, it is impossible to inverse a whole pixel having four sub-pixels comprised of red, first green, second green, and blue, which lowers the application range of the liquid crystal panel.